THURSDAY, Sept. 18 (HealthDay News) -- Not only do antibiotics not help pregnant women experiencing premature labor without ruptured membranes and no sign of infection, they may increase the risk of cerebral palsy in some children.

Two new studies followed children whose mothers had taken antibiotics at the end of their pregnancies. The children were followed up to the age of 7.

"This is a good study, because it's a large number of patients, and it shows that the use of antibiotics do not help and are possibly harmful for preterm labor in the absence of rupture of the membrane (broken water)," said Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City.

"There are other medications, but they really are not so effective in prolonging gestation for more than 48 hours," Wu added. "We still do not have a great solution for preterm delivery."

Which is not to say that all pregnant women should shun antibiotics.

"We need to reassure pregnant women that, if they have signs of infection and antibiotics are clearly indicated, then they should feel no reluctance to accept antibiotics," said Dr. Alan Fleischman, medical director of the March of Dimes.

In general, children born prematurely are at higher risk for cerebral palsy, various developmental difficulties and even death during the first month of life. Preterm birth with ruptured membranes has been linked with infection and inflammation.

"It's important to do a study like this in an attempt to decrease prematurity," Fleischman said. "There have been suggestions that use of antibiotics with the first signs of preterm labor could, in fact, stop preterm labor, because one of the causes of preterm labor, we believe, are low levels of infection that aren't obvious."

The new studies, published online Sept. 18 in the The Lancet, were follow-ups to original trials called ORACLE I and II. Those initial trials were done to see if possible underlying infection in women threatening to give birth prematurely could be helped by the antibiotics erythromycin and co-amoxiclav, delaying or preventing premature delivery. The initial results uncovered no increased risks to the children.

The new studies looked at children born to 3,298 women in the United Kingdom.

The researchers found that 4.4 percent of children whose mothers had taken both erythromycin and co-amoxiclav had cerebral palsy, compared with 1.6 percent of children whose mothers had only taken a placebo.

At this point, it's not clear if the risks apply to other antibiotics as well, the researchers said.

Some two in 1,000 children born at term develop cerebral palsy; the risk is higher for those babies born early. The risk for the children in this study was, overall, about two in every 100, while the risk for those whose mothers had taken one or both antibiotics was three-to-four per every 100 children, the researchers said.